From: Johan De Meersman
Date: October 12 2011 8:05am
Subject: Re: Index question
List-Archive: http://lists.mysql.com/mysql/226033
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----- Original Message -----
> From: "Tompkins Neil"
> Thanks for the information. One final question in what ways should we
> use EXPLAIN EXTENDED statement to help improve our query
> performance.
Explain is your friend. You should listen to it :-)
It gives a nice idea of how the database interprets your query, so you can see where the bottlenecks are, for example what bits don't use indices or cause file sorts.
The exact interpretation of it is an art, though, and there are many subtleties you only get by experience and reading documentation. It is not something that is quickly explained; it requires a good knowledge of how a database works on the inside.
--
Bier met grenadyn
Is als mosterd by den wyn
Sy die't drinkt, is eene kwezel
Hy die't drinkt, is ras een ezel
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